[ARM] 4215/1: s3c2410 usb device: per-platform vbus_draw

Introduce a platform_device (machine) specific callback function
which gets called when the amount of power we can draw from Vbus
has changed.

Signed-off-by: Harald Welte <laforge@openmoko.org>
Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>